Gas turbine rotors rotate at high speed and any unbalance causes vibration and reduces the life of the components. Therefore, it is known to balance such rotors by selective addition of weights.
Location of balance weights on collars attached to the disks involves the additional weight of the collar and elaborate machining of the collar. Such collars are conventionally of thin cross section and therefore susceptible to handling damage. Balance weights attached thereto are usually close tolerance highly machined parts.
Depending on the weight retention means, the weights can be improperly installed, endangering balance weight retention. Removal of the balance weights is often difficult, for instance involving drilling out of a rivet. The collar may be bent or otherwise damaged during this procedure. Often the balance weights are not positively trapped so that they may come off the collar or the collar itself may crack off causing substantial damage to the engine.
Location of the weights within the disk itself often creates complicated machining and possibly causes stress concentrations at highly stressed points. Such locations may interfere with the cooling passages for air cooled blades.
It is an object of the invention to balance a gas turbine rotor in a manner to facilitate blade air cooling.